FR2888962A1 - Animation creation method involves creating file comprising optimized requests for obtaining images from remote terminal, and description of different versions of animation and associated criterion - Google Patents

Abstract

The requests for obtaining images from a remote terminal are optimized by determining versions of the animation depending on criterion corresponding to characteristic of client liable to download the animation. A file comprising the optimized requests, and description of different versions of the animation and associated criterion, is created. Independent claims are also included for the following: (1) animation management method; (2) animation downloading method; (3) animation creation device; (4) animation management device; (5) animation downloading device; (6) digital data processing apparatus; and (7) information storage medium storing animation creating program.

Description

The present invention generally relates to animations, for example

  example built according to the technique called Flash developed by the company Macromedia.

  This technique makes it possible to make a file containing an animation that can be played on a computer.

  It is possible to include JPEG2000 image (s) in this animation. A description of this format is available at the internet address: http: llwww.jpeg.org.

  We are particularly interested in the creation of such an animation. The display quality of the animation depends directly on the number of keyframes. Indeed, the more keyframes there are, the less the interpolation number is large and therefore the higher the visual quality of the animation. However, the more key images to transmit, the higher the transmission rate, and the greater the computational cost to process the keyframes.

  It is therefore necessary to find a compromise between the quality of the animation on the one hand and the computing capacities and the bandwidth of the network on the other hand.

  In US 6 081 278, two versions of an animation are stored on a server. One version has a larger number of keyframes than the other.

  When a client terminal requests the animation, it sends its characteristics to the server which determines which version is best suited before sending this version.

  If many client terminals request an animation simultaneously, the compute load related to finding the version adapted to each client terminal may become too important for the server.

  US 6,442,603 discusses the case of a document containing several types of content such as text, audio, image, video. As in the previous document, when a client terminal requests the animation, it sends its characteristics to the server. The latter determines which types of data are compatible with the client terminal.

  This system has the same drawback as that of the previous document. In addition, it does not allow to modulate the quality in the same type of data.

  Low complexity video coding for receiver layered multicast, by S. Mc Canne, Jacobson and M. Vetterli, published in IEEE Journal of Selected Areas in Communications, Vol. 15, No. 6, August 1997, pages 983-1001, proposes a system in which the server has no active role in the choice of the quality level of the data sent to a client terminal.

  In this system, the server sends multiple hierarchy levels of a video stream to separate multipoint addresses. A client terminal subscribes to a number of levels. It starts by subscribing to the lowest hierarchy level and then tries to subscribe to higher levels as long as there is no loss.

  There is no server overhead. On the other hand, traffic related to the management of multipoint trees is high. In addition, it is necessary that routers compatible with the multipoint exist in the transmission networks. At present, very few of these routers exist on the Internet.

  Finally, the convergence time to the optimal quality level is high, which is not very compatible with Flash animations.

  Document US 6 185 625 proposes a method according to which the user of the client terminal sets the quality parameters that will be used to play the animation.

  This information is transmitted to the server, and the animation is coded specifically according to the parameters set by the user. The coded animation is then transmitted to the client terminal.

  This method therefore involves a specific encoding of the animation before it is transmitted. This can delay the transmission.

  In addition, the client terminal user must have technical knowledge to set the quality parameters appropriately.

  In US 6,442,658, an animation is considered as a set of segments. The segments are ranked according to their likelihood of being played after the current segment and also at an estimated transmission cost.

  Thus, a pre-loading is done according to the probability and the cost. The available memory of the client terminals can also be taken into account.

  The transmission time of the animation is reduced. However, this document does not propose a compromise between the quality of the animation on the one hand and the computing capacities and the bandwidth of the network on the other hand.

  Flash MX's Flash MX user guide, published by Dunod, describes the ActionScript language that allows a user to dynamically interact with an animation.

  The control that is possible is independent of the capabilities of the client terminals or the bandwidth.

  The present invention aims to overcome the drawbacks of the prior art, by providing a method and an animation creation device that allow a compromise between the quality of the animation on the one hand and / or the computing capabilities of a computer. terminal and the bandwidth of the transmission network on the other hand.

  To this end, the invention proposes a method for creating an animation comprising keyframes, characterized in that it comprises the steps of: determining a plurality of versions of the animation according to at least a criterion corresponding to at least one characteristic of the client able to download the animation, - creating a file comprising a description of the different versions determined and their associated criterion.

  The invention allows a fine adaptation of the animation to the capabilities of the client terminal and the available bandwidth.

  The computing load on the side of the server is reduced, since it is the client terminal that automatically determines the version that is adapted to it.

  Thus, there is no significant latency when downloading an animation. Indeed, even if there are many client terminals that request the animation simultaneously, the calculations are distributed on the client terminals.

  According to a first embodiment, the determination step comprises the steps of: assigning a priority level to each key image, calculating a global decoding cost of the key images of each priority level.

  In this case, the decoding cost is adapted to the computing capabilities of the client terminal that downloads the animation.

  According to a preferred characteristic, a version of the animation comprises keyframes to which the same priority level has been assigned.

  Thus, the number of keyframes to download varies depending on the priority level.

  According to a second embodiment, the determination step comprises the steps of: - determining several classes of client terminals according to their bandwidth, - determining a version of each key image for each class of client terminals.

  In this case, the bandwidth is taken into account. The download time of the animation is thus limited.

  Of course, it is possible to take into account both the computing capacity of the client terminals and the bandwidth.

  According to a preferred feature, the creation step includes determining requests for each keyframe for obtaining each keyframe from a remote terminal.

  According to a preferred characteristic, the requests are of the JPIP type.

  JPIP requests are established according to a protocol in the process of standardization, a description of which can be found at the Internet address: http: //www.jpeg.org.

  The invention also relates to a method of downloading an animation from a server to a client terminal, the animation having been created by the creation method presented above, characterized in that it comprises the steps of: receiving the description of the different versions of the animation, selecting a version of the animation according to at least one characteristic of the client terminal, sending requests according to the version selected.

  According to the first embodiment, the selection step comprises the steps of: determining a priority level of the animation according to the global decoding cost of the key images of each priority level and the processing capabilities of the client terminal, - selection of keyframes belonging to the determined priority level.

  According to the second embodiment, the selection step comprises the steps of: determining the effective bandwidth of the client terminal, identifying the class of the client terminal as a function of its effective bandwidth, selecting versions of the client terminals; keyframes corresponding to the class of the client terminal.

  Correlatively, the invention relates to a device for creating an animation comprising keyframes, characterized in that it comprises: means for determining a plurality of versions of the animation according to at least one corresponding criterion at least one characteristic of the client capable of downloading the animation, means for creating a file comprising a description of the different versions determined and their associated criterion.

  The invention also relates to a device for downloading an animation from a server to a client terminal, the animation having been created by the previous authoring device, characterized in that it comprises: means for receiving the description of the different versions of the animation; means for selecting a version of the animation according to a characteristic of the client terminal; means for sending requests according to the selected version.

  The devices according to the invention comprise means for implementing the characteristics previously described.

  The authoring device, the method and the downloading device have advantages similar to those previously presented.

  The invention also relates to a file comprising the coding data of an animation created by the creation method previously presented, characterized in that it comprises an indexing, a sequence of requests, a priority and a display instant, for each keyframe, and in addition the computational cost of each priority level.

  The invention also relates to a file comprising the encoding data of an animation created by the creation process previously presented, characterized in that it comprises an indexing, a sequence of queries classified according to the classes of client terminals and a time display, for each keyframe, and further defining the classes.

  The invention also relates to a digital apparatus including the device according to the invention or means for implementing the method according to the invention. This digital camera is for example a digital camera, a digital camcorder, a scanner, a printer, a photocopier, a fax machine. The advantages of the device and the digital device are identical to those previously exposed.

  An information storage means, readable by a computer or by a microprocessor, integrated or not to the device, possibly removable, stores a program implementing the method according to the invention.

  A computer program readable by a microprocessor and comprising one or more sequences of instructions is able to implement the methods according to the invention.

  The features and advantages of the present invention will become more apparent upon reading a preferred embodiment illustrated by the accompanying drawings, in which: FIG. 1 is an embodiment of a device implementing FIG. invention, - figure 2 represents a device according to the invention, - figure 3 represents a first embodiment of animation creation method according to the invention, - figure 4 represents a graphical interface used in the method of FIG. 5 represents a file containing an animation according to the invention; FIG. 6 represents an embodiment of calculation of a computational cost included in the method of FIG. 3; FIG. first embodiment of an animation download method according to the invention, FIG. 8 represents an embodiment of determining priority levels, included in the method of FIG. 9 shows a second embodiment of an animation creation method according to the invention; FIG. 10 represents a file containing an animation according to the invention; FIG. 11 represents an embodiment 1 is a picture transmission pattern included in the method of FIG. 9, FIG. 12 represents an image list structure, FIG. 13 shows an embodiment of determination of different versions of an image respecting a predetermined bandwidth, - Figure 14 shows a second embodiment of animation download method according to the invention.

  According to the embodiment chosen and represented in FIG. 1, a server 1 is connected to client terminals 2, only one of which is represented, via a communication network 3.

  The server 1 and the client terminal 2 are computers, an exemplary architecture of which is described below.

  The connection between the two devices is conventional and will not be described here. It is for example of type http. It is assumed that the data transmission is performed without loss.

  The server 1 comprises a unit 10 for receiving requests from the client terminal 2. It also comprises a unit 11 for transmitting digital data to the client terminal 2.

  The request receiving unit 10 transmits the received requests to the processing unit 12. The processing includes the identification of the required data, their formatting and their transmission through the unit 11.

  The server 1 also comprises a memory 13 in which data are stored. A control unit 14 controls the operation of the units of the server 1.

  According to the invention, the server 1 comprises a unit 15 for creating an animation, which comprises: means for determining a plurality of versions of the animation according to at least one criterion corresponding to at least one characteristic of the client likely to download the animation, means for creating a file comprising a description of the different versions determined and their associated criterion.

  The client terminal 2 comprises a unit 20 sending requests to the server 1. It also comprises a unit 21 for receiving digital data from the server 1.

  The unit 21 transmits the received data to the processing unit 22. The treatment, object of the present invention, is detailed in the following using algorithms.

  According to the invention, the unit 21 receives the description of the different versions of the animation. The unit 22 selects a version of the animation according to at least one characteristic of the client terminal. Finally, unit 20 issues requests based on the selected version.

  The client terminal 2 also includes a memory 23 in which data are stored. A control unit 24 controls the operation of the units of the client terminal 2.

  According to the embodiment chosen and shown in FIG. 2, a device embodying the invention is for example a microcomputer 10 connected to different peripherals, for example a digital camera 107 (or a scanner, or any means of acquisition or image storage) connected to a graphics card and providing information to be processed according to the invention.

  The device 10 comprises a communication interface 112 connected to a network 113 able to transmit digital data to be processed or conversely to transmit data processed by the device. The device 10 also comprises a storage means 108 such as for example a hard disk. It also comprises a disk drive 110 110. This disk 110 may be a diskette, a CD-ROM or a DVD-ROM, for example. The disk 110 as the disk 108 may contain data processed according to the invention as well as the program or programs implementing the invention which, once read by the device 10, will be stored in the hard disk 108. According to a variant, the program allowing the device to implement the invention, can be stored in ROM 102 (called ROM in the drawing). In the second variant, the program can be received to be stored in a manner identical to that previously described via the communication network 113.

  The device 10 is connected to a microphone 111. The data to be processed according to the invention will in this case be an audio signal.

  This same device has a screen 104 making it possible to display the data to be processed or to interface with the user who can thus set up certain modes of treatment, using the keyboard 114 or by any other means (mouse for example) .

  The CPU 100 (called the CPU in the drawing) executes the instructions relating to the implementation of the invention, instructions stored in the read-only memory 102 or in the other storage elements. When powering up, the processing programs stored in a non-volatile memory, for example the ROM 102, are transferred into the RAM RAM 103 which will then contain the executable code of the invention as well as registers for storing the variables. necessary for the implementation of the invention.

  More generally, an information storage means, readable by a computer or by a microprocessor, integrated or not into the device, possibly removable, stores a program implementing the method according to the invention.

  The communication bus 101 allows communication between the various elements included in the microcomputer 10 or connected to it. The representation of the bus 101 is not limiting and in particular the central unit 100 is able to communicate instructions to any element of the microcomputer 10 directly or via another element of the microcomputer 10.

  FIG. 3 represents a first embodiment of a method for creating an animation, according to the invention. This method is implemented in the authoring device and comprises steps E1 to E8.

  The method is embodied in the form of an algorithm that can be stored in whole or in part in any information storage means capable of cooperating with the microprocessor. This storage means is readable by a computer or a microprocessor. This storage means is integrated or not to the device, and can be removable. For example, it may comprise a magnetic tape, a floppy disk or a CD-ROM (compact disk with frozen memory).

  Step El is the selection of an IM image to serve as a basis for the animation. The image is coded according to the JPEG 2000 standard which allows quick and easy access to different resolutions, qualities and regions of interest of the image.

  The animation is created from this single image. Alternatively, the animation is created from several images.

  The next step E2 is the definition of the keyframes IMn of the animation, with n an integer varying between 1 and an integer N. For this, the user uses a graphical interface. This interface is for example generated by using the C ++ QT GUI design library proposed by the company TrollTech, available at the Internet address: http: / / www.trolltech.com.

  This interface has several windows. As shown in Figure 4, window A displays the original size of the image. Window B displays the size of the image after modification. Windows C and D allow you to change the size of the image. A new size expressed in pixels can be defined in the window C or a new size expressed as a percentage of the size of the initial image can be defined in the window D. It should be noted that in the preferred embodiment of the invention, only sizes corresponding to the resolutions defined in the original image can be chosen.

  Window E allows you to choose the quality of the image. For example, the images have nine levels of quality.

  The window F makes it possible to indicate that a rectangular area H of the image IM will be selected.

  The window J makes it possible to fix the instant of display of the image.

  The next step E3 is the definition of a priority level Pn for each key image IMn. The priority level of a keyframe depends on its importance. An image that can be approximated by interpolation between two other images receives a low priority level. An image that would be degraded by an interpolation approximation receives a higher priority. An image that can not be interpolated receives an even higher priority.

  Eight levels of priority PI to P8 are for example available. Level 1 is the highest priority level. The priorities are decreasing to level 8. The user sets the priority level of the image through the window G (Figure 4).

  The next step E4 is the calculation for each key image IMn of requests Rn1, Rn2, ... according to the JPIP protocol. The JPIP protocol for transmitting data coded according to the JPEG2000 standard enables a remote terminal to repatriate an image.

  A list of JPIP requests is thus formed and stored in a file intended to be downloaded, interpreted and played on a client terminal. This file, or animation script, is for example in SWF format. JPIP requests are established according to a protocol in the process of standardization, a description of which can be found at the Internet address: http: llwww. jpeg.org.

  For each keyframe, information relating to the size, resolution, quality, selected area, which were defined in step E2 are inserted in the JPIP queries.

  The next step E5 is the definition, using the window J, of a display time Tn for each key image IM. An instant of display is a time in seconds, determined from the beginning of the animation. During the subsequent execution of the animation, each image is displayed at the defined time.

  The next step E6 is the calculation of the global decoding cost cck of each priority level Pk with k an integer varying between 1 and 8. The global decoding cost cck of a priority level Pk is the decoding cost of the images key of the given priority level, and interpolation of the other images from these keyframes.

  For this, a computer program analysis tool, such as the one called Quantify from Rational Software Corporation, described on the Internet address http: / / www.rational.comlproductslquantify ntl, determines the number of elementary operations performed during the execution of the program and the execution time of the program.

  The number of elementary operations performed per second is then calculated by dividing the first result by the second.

  Alternatively, the Time command in Unix and Linux operating systems can determine the computational cost of a program.

  An embodiment of step E6 is detailed below.

  The next step E7 is the storage of the data relating to the animation in a FIM file represented in FIG. 5. This file comprises, for each key image IM ,, the indexing n, the sequence of requests JPIP the priority Pr, and the instant of display Tn.

  It also includes the computational cost cck of each priority level.

  The next step E8 is the storage of the previous file on the server.

  The step E6 of determining a computational cost for each priority level of an animation is now detailed with reference to FIG. 6, in the form of an algorithm comprising steps E60 to E64.

  Step E60 is an initialization to which a variable k is initialized to the value one. The variable k represents the current priority level.

  The next step E61 is a test to determine if the variable k is less than or equal to the number of priority levels. If the answer is positive, this step is followed by the step E62 at which the computational cost Ck of decoding the animation by considering only the priority levels from 1 to k is calculated. As previously stated, this cost is calculated with a program analysis tool known in itself.

  The next step E63 is the calculation of the computational cost cck of the current level. For this, the computational cost Ck calculated in the previous step is reduced by the computational cost Ck-1 calculated during the previous iteration. Of course, during the first pass through this step (k = 1), the quantity Ck_1 is zero.

  In the next step E64, the variable k is incremented by one unit. This step is followed by step E61 previously described.

  When the answer is negative in step E61, the computational costs of all the priority levels of the animation have been determined.

  FIG. 7 represents a first embodiment of a method of downloading an animation, according to the invention. This method is implemented in the client terminal 2 and comprises steps E10 to E19.

  The method is embodied in the form of an algorithm that can be stored in whole or in part in any information storage means capable of cooperating with the microprocessor. This storage means is readable by a computer or a microprocessor. This storage means is integrated or not to the device, and can be removable. For example, it may comprise a magnetic tape, a floppy disk or a CD-ROM (compact disk with frozen memory).

  Step El0 is sending a request to the server to obtain the description file of the animation.

  The next step El 1 is the reception of the description file.

  The next step E12 is the search for the highest priority level possible according to the decoding cost of each priority level and the processing capabilities of the client terminal. This step is detailed below.

  The next step E13 is a compatibility test of the animation with the client terminal. If no priority level is compatible with the client terminal, a logical variable COMP is set to false. Otherwise, this variable is set to true.

  The next step E14 is a test on the value of the logical variable COMP.

  If it indicates an incompatibility, this step is followed by step El 5 which is the display of an error message.

  If there is compatibility in step E14, this step is followed by step E16 which is the sending of JPIP requests corresponding to the level of priority 20 previously determined. The next step E17 is the reception and decoding of the data received in

response to queries issued.

  The next step E18 is an interpolation between the received keyframes, if it is necessary to be able to play the animation at 25 frames per second. The interpolation is classic. It is weighted according to the distance between the interpolated image and the keyframes used for the interpolation.

  The next step E19 is the display of the animation at a rate of 25 frames per second on the client terminal.

  The search step E12 of the highest priority level possible according to the decoding cost of each priority level and the processing capabilities of the client terminal is now detailed with reference to FIG. 8, in the form of an algorithm having steps E120 to E126.

  Step E120 is an initialization at which the number K of priority levels defined in the animation is read. A variable k is initialized to one. The variable k represents a current priority level. A variable C is also initialized to the value zero. Variable C represents the cumulative computational costs of the different levels.

  The CPU calculation capacity of the client terminal expressed as the number of elementary operations per second is read in the memory 112.

  The next step E121 is a test to determine if there is still at least one priority level to consider. If the answer is positive, this step is followed by the step E122 in which the cumulation C of the computational costs is increased by the computational cost of the current priority level.

  The next step E123 is a test to determine whether the computational cost C is less than the CPU capacity of the client terminal. If the answer is positive, it means that the client terminal has a capacity greater than the determined computational cost. This step is then followed by the step E124 at which the variable k is incremented by one unit to consider a next priority level.

  Step E124 is followed by step E121 previously described.

  When the answer is negative in step E123, this means that the computing capacity of the client terminal is lower than the computed cost determined. In this case, the step E123 is followed by the step E125, in which the JPIP requests corresponding to the priority levels of ranks lower than that of the current level Pk are transmitted to the communication interface of the client terminal.

  When the answer is negative in step E121, this means that the computing capacity of the client terminal is greater than the computational cost of all the priority levels of the animation. In this case, the step E121 is followed by the step E126, to which the JPIP requests corresponding to all the priority levels of the animation are transmitted to the communication interface of the client terminal.

  FIG. 9 represents a second embodiment of a method for creating an animation, according to the invention. This method is implemented in the creation device and comprises steps E20 to E28.

  The method is embodied in the form of an algorithm that can be stored in whole or in part in any information storage means capable of cooperating with the microprocessor. This storage means is readable by a computer or a microprocessor. This storage means is integrated or not to the device, and can be removable. For example, it may comprise a magnetic tape, a floppy disk or a CD-ROM (compact disk with frozen memory).

  Step E20 is the definition of several classes of client terminals. The user has a graphical interface to select different bandwidth values representing the actual throughput between the server and a client terminal. For example, three classes CL1, CL2 and CL3 are created.

  The next step E21 is the storage of the bandwidth thresholds defining the client terminal classes.

  The next step E22 is the selection and definition of the IMn keyframes of the animation. One or more images encoded according to the JPEG2000 standard are selected, and keyframes are formed. The construction of the keyframes can be done with a graphical interface of the type of that presented in the first embodiment. Alternatively, the construction of the keyframes can be done through a content authoring tool such as Macromedia Flash content creation software Flash MX. This tool is available via the Internet at: http: //www.macromedia. com / software / flash /.

  The book entitled Flash MX by Guylaine Monnier, published by Dunod, Paris, 2002, describes this software.

  A display time Tn for each keyframe is determined. An instant of display is a time in seconds, determined from the beginning of the animation.

  The next step E23 is the calculation of the transmission cost of each key image 1Mn. The transmission cost of a key image IMn is the Dn rate required for transmission. The rate Dn is equal to FxSn, where F is the temporal resolution of the animation, expressed in s "and Sn is the size of the key image considered, expressed in bits.

  Transmission costs are stored in this step.

  The next step E24 is a detection of any key images posing a transmission problem.

  For each class of clients, corresponding to a maximum bandwidth, it is investigated whether there are images that exceed the maximum bandwidth so that the transmission time between the server and a client terminal is incompatible with a display of good quality. the animation on the client terminal.

  This step is detailed below. It results in a list L15 of images not compatible with the maximum bandwidths of the different classes.

  The next step E25 is the calculation, for each image in the list L, of a set of couples (bit rate, distortion) for each version (resolution, quality) of the image. This step is detailed below.

  The next step E26 is the calculation of the JPIP requests of each key image IMn, which will allow each class CL1 to CL3 of clients to obtain the version of the keyframe adapted to the bandwidth which it has.

  For a given keyframe, it is necessary to retrieve the information relating to the size, the resolution, the quality, and the zone possibly selected in the keyframe. It is then necessary to check if this key image belongs to the list L of the key images posing a transmission problem.

  If the current keyframe does not belong to the list L, the previous information is inserted into the data fields of the JPIP queries.

  If the current keyframe belongs to the list L, then the associated JPIP queries concern a degraded version of the keyframe, and not the initial keyframe.

  Classes are considered one after the other. For a given class corresponding to a given bandwidth, and for a given keyframe, consider the version (resolution and quality) of this image whose bit rate is compatible with the bandwidth and whose distortion is minimal.

  This version is obtained as a result of the previous step E25.

  The JPIP request of this version is formed and stored in the description file.

  The next step E27 is the storage of the data relating to the animation in an FF file represented in FIG. 10. This file comprises, for each key image IMn, indexing n, the sequence of JPIP requests Rn1, Rn2 ,. .. classified according to the client terminal classes and the display time Tn.

  It further includes the definition of classes CL1 to CL3.

  The next step E28 is the storage of the FF file on the server.

  An embodiment of step E24 for determining images that do not respect the bandwidth is described with reference to FIG. 11, in the form of an algorithm comprising steps E240 to E250.

  Step E240 is the reading of the value of the frequency F of display of the images of the animation.

  The next step E241 is the creation of an empty L list. The list L is associated with a table T illustrated in FIG. 12, containing data on each image exceeding one of the maximum bandwidths of the client classes.

  For each image in the list L, the following data are stored in the table T: the time index of the image, the index of the lowest possible bandwidth client class for which the image is not poses no problem, - its size in bytes, - the size at which the creator of the animation wishes to display the image in the animation, 2888962 20 - the quality level Qumax set by the creator.

  A variable i is initialized to the value one. The variable i represents the index of the current CL client class ;. We first consider the class corresponding to the lowest bandwidth, then the classes with increasing bandwidth.

  The next step E242 is the reading of the value of the maximum bandwidth BPmax associated with the current class CL; In addition, an available bandwidth LBP is due to the low cost of transmitting the interpolation parameters between two keyframes. The available bandwidth ABP depends on the current maximum bandwidth BPmax, the number of interpolated images between two keyframes, the number of bits needed to represent the interpolation parameters and the frequency of the animation.

  The next step E243 is an initialization at which a parameter m is initialized to consider the first key image IMm posing a transmission problem for the class processed at the previous iteration. During the first pass through this step, we consider the first keyframe of the animation.

  The next step E244 is reading the size Dm in bytes of the current image.

  The next step E245 is a test to determine if the current image respects the BPmax bandwidth. This is to check if the image can be transmitted in less than 11F. For this, we check if the inequality: F.Dm <BPmax + L1sP is checked.

  If the answer is negative, it means that the IMm current image does not respect the bandwidth. In this case, the step E245 is followed by the step E246 in which the current image IMm is entered in the list L, with the data previously stated.

  If the answer is positive in step E245, this means that the current image IMm respects the bandwidth. In this case, step E245 is followed by step E247 which is a test to check if there is at least one keyframe of the animation to be processed.

  If the answer is positive, then this step is followed by step E248 to consider the next keyframe. Step E248 is followed by step E244 previously described.

  If the answer is negative in step E247, then this step is followed by step E249 which is a test to determine if the list L is empty for the current class and if there is still at least one class to be processed.

  As long as the answer is negative to these two tests, step E249 is followed by step E250 to consider the next class.

  Step E250 is followed by step E242 previously described.

  When the response is positive to at least one of the two tests of step E249, the processing is complete.

  An embodiment of step E25 for estimating the quality of different versions of an image of list L is described with reference to FIG. 13, in the form of an algorithm comprising steps E300 to E315.

  An image of the list L is considered here. The step E300 is the reading of the temporal index of this image. The next step E301 is the reading of the coded picture. A JPEG2000 decoder then retrieves high level information relating to this image.

  This information is: - the maximum spatial resolution of the image HxW, where H and W are the height and the width of the image expressed in number of pixels.

  the number of Rmax resolution level used to represent the image.

  The next step E302 is the calculation of the image size and the number of resolution levels that are used in the next processing. The size is given by the formulas: h = min (H, hu) w = min (W, wu) where hu and wu are the height and the width of the image expressed in number of pixels, fixed by the creator of the 'animation.

  The number of levels of resolution is provided by the formulas: Rumax = min (R (h, w), Rmax), where R (h, w) is the level of resolution for which the image has a height and a width respectively less than or equal to the height h and the width w.

  The next step E303 is the decoding of the image at the Rumax resolution and the Qumax quality level.

  The next step E304 is the storage of the image thus decoded and reconstructed Iv (Rumax, Qumax) to serve as a reference image.

  The next step E305 is an initialization in which two variables R and Q are initialized to the value zero. The variable R represents the current resolution level and the variable Q represents the current quality level. The zero value for these two variables corresponds to the lowest resolution and quality levels.

  The next step E306 is obtaining the image Iv (R, Q) corresponding to the current resolution level R and to the current quality level Q. The image Iv (R, Q) is obtained by a JPIP request.

  The next step E307 is the data storage 20 corresponding to the image Iv (R, Q) in the table T associated with the list L (FIG. 12).

  These data are: - the size D (Iv (R, Q)) of the image Iv (R, Q), expressed in bytes, - the current resolution level R, - the current quality level Q. The step next E308 is the decoding of the current image Iv (R, Q). The next step E309 is an enlargement of the decoded current image to form an enlarged image Iv (Rumax, Q) at the Rumax resolution.

  Of course, if the R and Rumax resolutions are equal, there is no magnification.

  The next step E310 is a comparison of the enlarged image Iv (Rumax, Q) with the reference image Iv (Rumax, Qumax). Thus, the quality degradation of the animation is estimated, in the case of the replacement of the reference image by the enlarged image Iv (Rumax, Q).

  This estimate is for example the mean square deviation between the two images. In step E311, the result Dist (Iv (R, Q)) of the estimate is stored in the table T associated with the list L (FIG. 12).

  The next step E312 is a test to determine if the current quality Q is strictly less than the Qumax value. If the answer is positive, then this step is followed by step E313 at which the quality Q is incremented by one. Step E313 is followed by step E306 previously described.

  If the answer is negative in step E312, then this step is followed by step E314, which is a test to determine if the current resolution R is strictly less than the Rumax value. If the answer is positive, then this step is followed by the step E315 at which the resolution R is incremented by one unit and the current quality Q is set to zero. Step E315 is followed by step E306 previously described.

  If the answer is negative in step E314, then all possible versions of the considered image of the list L have been determined.

  This processing is repeated for all the images in the list L. FIG. 14 represents a second embodiment of a method of downloading an animation, according to the invention. This method is implemented in the client terminal 2 and comprises steps E500 to E510.

  The method is embodied in the form of an algorithm that can be stored in whole or in part in any information storage means capable of cooperating with the microprocessor. This storage means is readable by a computer or a microprocessor. This storage means is integrated or not to the device, and can be removable. For example, it may comprise a magnetic tape, a floppy disk or a CD-ROM (compact disk with frozen memory).

  Step E500 is sending a request to the server to obtain the description file of the animation.

  The next step E501 is the reception of the description file.

  The next step E502 is the recovery of the effective bandwidth of the client terminal 2. This operation is performed either from a configuration file or by request to the user by means of a graphical interface.

  The next step E503 is an identification of the class of the client terminal from the description of the animation and according to its bandwidth. The keyframe versions corresponding to the client terminal class are selected.

  The next step E504 is a compatibility test of the animation with the client terminal. If the client terminal does not have enough bandwidth for the animation, a logical variable COMP is set to false. Otherwise, this variable is set to true.

  The next step E505 is a test on the value of the logical variable COMP.

  If it indicates an incompatibility, this step is followed by the step E506 which is the display of an error message.

  If there is compatibility in step E505, this step is followed by step E507 which is the issuing of JPIP requests corresponding to the class 20 previously determined.

  The next step E508 is the reception and decoding of the received data in response to the transmitted requests.

  The next step E509 is an interpolation between the received keyframes, if it is necessary to be able to play the animation at 25 frames per 25 seconds.

  The next step E510 is the display of animation at a rate of 25 frames per second on the client terminal.

  Of course, the present invention is not limited to the embodiments described and shown, but encompasses, on the contrary, any variant within the scope of those skilled in the art.

  In particular, the two embodiments are combinable. We take into account when creating the bandwidth animation of the client terminals and assign a priority level to each key image.

Claims (24)

  A method of creating an animation comprising keyframes, characterized in that it comprises the steps of: determining (E3, E4, E6) a plurality of versions of the animation according to at least a criterion corresponding to at least one characteristic of the client able to download the animation, - creation (E7) of a file comprising a description of the different versions determined and their associated criterion.   2. A method of creating an animation according to claim 1, characterized in that the determining step comprises the steps of: assigning (E3) a priority level to each keyframe, - calculating (E6) of a global decoding cost of the keyframes of each priority level.   3. A method of creating an animation according to claim 2, characterized in that a version of the animation comprises keyframes to which the same level of priority has been assigned.   4. A method of creating an animation according to any one of claims 1 to 3, characterized in that the determining step comprises the steps of: - determining (E20) of several classes of client terminals according to their bandwidth, - determining (E24, E25) a version of each keyframe for each class of client terminals.   5. A method of creating an animation according to any one of claims 1 to 4, characterized in that the creation step (E4, E26) comprises the determination of requests for each keyframe, intended to obtain each key image from a remote terminal.   6. Method according to claim 5, characterized in that the 5 requests are JPIP type.   7. A method of downloading an animation from a server to a client terminal, the animation having been created by the creation method according to any one of claims 1 to 6, characterized in that it comprises the steps of: - reception (E11, E501) of the description of the different versions of the animation, - selection (E12, E503) of a version of the animation according to at least one characteristic of the client terminal, - transmission ((E16 , E507) of requests based on the selected version.   8. The downloading method as claimed in claim 7, characterized in that the selection step (E12) comprises the steps of: determining a priority level of the animation as a function of the overall decoding cost of the key images of each priority level and processing capabilities of the client terminal, - selecting the keyframes belonging to the determined priority level.   9. Download method according to claim 7 or 8, characterized in that the selection step comprises the steps of: -determination (E502) of the effective bandwidth of the client terminal, -identification (E503) of the class of the terminal client according to its effective bandwidth, - selection (E503) of the keyframe versions corresponding to the class of the client terminal.   10. Device for creating an animation comprising key images, characterized in that it comprises: means (15) for determining a plurality of versions of the animation according to at least one corresponding criterion at least one characteristic of the client capable of downloading the animation; means (15) for creating a file comprising a description of the different versions determined and their associated criterion.   11. Device for creating an animation according to claim 10, characterized in that the determining means comprise: means for assigning a priority level to each key image, means for calculating a global decoding cost of the keyframes of each priority level.   12. Device for creating an animation according to claim 11, characterized in that the determination means are adapted to form a version of the animation comprising keyframes to which the same level of priority has been assigned.   13. Device for creating an animation according to any one of claims 10 to 12, characterized in that the determination means comprise: means for determining several classes of client terminals as a function of their bandwidth; means for determining a version of each keyframe 30 for each class of client terminals.   14. Device for creating an animation according to any one of claims 10 to 13, characterized in that the creation means comprise means for determining requests for each key image, intended to obtain each keyframe from a remote terminal. .   15. Device according to claim 14, characterized in that the means for determining requests are adapted to form queries JPIP type.   16. Device for downloading an animation from a server to a client terminal, the animation having been created by the authoring device according to any one of claims 10 to 15, characterized in that it comprises: - means (21) receiving the description of the different versions of the animation, - means (22) for selecting a version of the animation according to at least one characteristic of the client terminal, - means (20) ) to issue requests based on the selected version.   17. Download device according to claim 16, characterized in that the selection means (22) comprise: means for determining a priority level of the animation as a function of the overall decoding cost of the key images of each level of priority and processing capabilities of the client terminal; - means for selecting keyframes belonging to the determined priority level.   18. Download device according to claim 16, characterized in that the selection means (22) comprise: means for determining the effective bandwidth of the client terminal; means for identifying the class of the client; client terminal according to its effective bandwidth; means for selecting versions of the keyframes corresponding to the class of the client terminal.   19. Apparatus for creating an animation according to any one of claims 10 to 15, characterized in that the determination and creation means are incorporated in: - a microprocessor (100), - a read-only memory (102) comprising a program for processing the data, and a random access memory (103) having registers adapted to record modified variables during the execution of said program.   20. Download device according to any one of claims 16 to 18, characterized in that the receiving means, selection and transmission are incorporated in: - a microprocessor (100), a read-only memory (102) comprising a program for processing the data, and - a RAM (103) having registers adapted to record modified variables during the execution of said program.   21. Apparatus for processing (10) digital data, characterized in that it comprises means adapted to implement the method according to any one of claims 1 to 9.   22. Apparatus for processing (10) digital data, characterized in that it comprises the device according to any one of claims 10 to 20.   23. File containing the encoding data of an animation created by the creation method according to claim 2 or 3, characterized in that it comprises an indexing (n), a sequence of requests (Rn1, Ri2), a priority (Pn) and a display instant (Tn), for each key image (IMn), and further the computational cost (cck) of each priority level.   24. File comprising the coding data of an animation created by the creation method according to claim 4, characterized in that it comprises an indexing (n), a sequence of requests (Rn1, Rn2) classified according to the classes. client terminals and a display instant (Tn), for each key image Mn), and further defining the classes (CL, CL3).